The MSS laboratory hypothesis is that prosurvival, angiogenesis and motility signals converge at common pathways in the local tumor microenvironment. This Section has focused on the role of Ca++ as a regulator of gene expression and cellular physiology, and application of novel technologies to pathway discovery in epithelial ovarian cancer. We continue to study the signal transduction function of the cytosolic signaling protein CAIR-1/BAG-3. Clinical correlative studies are ongoing to assess the role of CAIR-1 expression in epithelial cancers. These are being driven by dissection of protein functional domains and their cognate parters. Our hypothesis that CAIR-1 should function downstream of a calcium-regulated or calcium-associated pathways led to the identification of phospholipase C-gamma (PLC-g) as a putative partner protein. CAIR-1 binds to PLC-g under basal conditions and is dissociated when cells are stimulated with epidermal growth factor. This binding requires the CAIR-1 PXXP binding to the SH3 domain of PLC-g. Binding to HSP-70 occurs through the BAG domain, C-terminal to the PXXP region and is not EGF sensitive. The role of the BAG domain is under investigation using domain deletion mutants on a MDA435 human breast cancer cell background. These studies include in vitro HSP-70 pathway studies as well as the soon to be initiated xenograft studies. Pathway regulation studies in ovarian cancer have used both CGAP cDNA libraries generated in our laboratory from microdissected ovarian cancer epithelium, and application of novel proteomic technologies including 2-D gels, micro-Western analysis, and protein microarrays. A relatively new growth factor, granulin-epithelin precursor (GEP) was shown to be differentially expressed between invasive ovarian cancer and tumor of low malignant potential. This finding was validated in a series of patient samples by RT-PCR and immunohistochemistry. Stable anti-sense GEP transfection into ovarian cancer cell lines reduces proliferative capacity in vitro. Using proteomics, we have demonstrated a similar differential expression of RhoGDI, a protein key in regulation of actin organization and subsequent cytoskeletal function. Further studies are ongoing to characterize these proteins in ovarian cancers.